Cooling unit, processing chamber, part in the processing chamber, and cooling method

ABSTRACT

A cooling unit for cooling a target object to a target temperature includes a decompression chamber thermally connected to the target object; a spraying part which sprays a liquid heat medium having a temperature equal to or lower than the target temperature to an inner surface of the decompression chamber; and an electric field generator which generates an electric field such that the heat medium sprayed from the spraying part is attached to the inner surface of the decompression chamber. The cooling unit further includes an exhaust part which evacuates the decompression chamber such that a pressure in the decompression chamber is equal to or lower than a saturated vapor pressure of the heat medium at the target temperature.

FIELD OF THE INVENTION

The present invention relates to a cooling unit and a cooling method for controlling a temperature of a target object to be cooled to and be maintained at a target temperature, and a processing chamber and a part in the processing chamber forming the cooling unit.

BACKGROUND OF THE INVENTION

In a semiconductor manufacturing apparatus, a plasma is frequently used to perform a processing such as an etching on a semiconductor wafer as a target object to be processed. However, the semiconductor wafer or the wall of a processing chamber may be unnecessarily heated by the plasma to a high temperature. Further, although there is a semiconductor manufacturing apparatus in which the semiconductor wafer needs to be processed at a high temperature, cooling is required after the processing for transferring and for another processing even in such apparatus. Accordingly, the semiconductor manufacturing apparatus includes a cooling unit for cooling the semiconductor wafer, the wall of the processing chamber, high-temperature members and the like. The cooling unit performs cooling by circulating liquid for cooling (hereinafter, referred to as a heat medium) in a flow path formed in, e.g., a mounting table on which the semiconductor wafer is mounted (see, e.g., Japanese Patent Application Publication Nos. 2001-44176 and H7-235588). A cooling method using the circulation of the heat medium is referred to as a forced convection heat transfer method.

However, in cooling through the forced convection heat transfer method, since there are certain limitations on the heat transfer characteristics of the flow path, it is difficult to uniformly cool the semiconductor wafer or the like, and responsiveness to temperature control is poor. In order to increase an amount of heat exchange between the heat medium and the cooling unit, e.g., fins may be provided in the flow path to improve the heat transfer characteristics of the flow path. However, since the heat transfer characteristics of the flow path is inversely related to the pressure loss, if the heat transfer characteristics of the flow path are increased, the pressure loss in the flow path becomes large, thereby increasing energy consumption of a pump for delivering the heat medium. On the other hand, if the pressure loss is reduced in order to promote energy saving, a difference between a temperature at the inlet and that at the outlet of the heat medium becomes large, and the heat transfer characteristics of the flow path are degraded, thereby making it difficult to uniformly cool the semiconductor wafer.

In order to overcome the above problems, the inventors of the present invention have designed a cooling unit capable of achieving high uniformity, high heat transfer, high responsiveness and energy saving in cooling a semiconductor wafer, compared to a conventional cooling method, by spraying a liquid heat medium to a desired location of the inner surface (inner side wall, inner top surface, inner bottom surface) of a decompression chamber formed in a mounting table, and controlling the inner pressure of the decompression chamber to induce a phase change in the heat medium on the inner surface. As described above, a cooling method using a phase change in the heat medium is referred to as a phase change heat transfer method or vacuum vaporization cooling method.

However, from results of experiments, in a configuration in which the heat medium is simply sprayed to the inner surface of the decompression chamber at a low pressure, since there is no component for actively attracting the heat medium to the inner surface of the decompression chamber, the heat medium is expected to be randomly attached to the inner surface of the decompression chamber. Accordingly, it is difficult for the liquid heat medium to be attached to the inner surface. Therefore, it causes a new problem that it is required to supply into the decompression chamber a larger amount of heat medium than that of heat medium needed theoretically.

Further, if the amount of heat medium is increased, although the liquid heat medium may be attached to the inner surface of the decompression chamber, the heat medium supplied into the decompression chamber may not be sufficiently evacuated. In this case, the heat medium attached to the inner surface of the decompression chamber is less likely to undergo a phase change, thereby causing a problem that it is difficult to effectively cool the mounting table.

SUMMARY OF THE INVENTION

In view of the above, the present invention provides a cooling unit and cooling method capable reducing an amount of heat medium required for vacuum vaporization cooling, and cooling a target object with high efficiency, by using an electric field which attracts the heat medium sprayed into a decompression chamber thermally connected to the target object to an inner surface of the decompression chamber, and further provides a processing chamber and a part in the processing chamber forming the cooling unit.

In accordance with one aspect of the present invention, there is provided a cooling unit for cooling a target object to a target temperature, including: a decompression chamber thermally connected to the target object; a spraying part which sprays a liquid heat medium having a temperature equal to or lower than the target temperature to an inner surface of the decompression chamber; an electric field generator which generates an electric field such that the heat medium sprayed from the spraying part is attached to the inner surface of the decompression chamber; and an exhaust part which evacuates the decompression chamber such that a pressure in the decompression chamber is equal to or lower than a saturated vapor pressure of the heat medium at the target temperature.

The spraying part may have a nozzle for spraying the heat medium into the decompression chamber, and the heat medium is electrically charged by friction between the nozzle and the heat medium.

Preferably, the cooling unit may further include a voltage application part which applies a voltage to the spraying part.

The decompression chamber may be formed in the target object.

It is preferred that the decompression chamber may be provided outside the target object and is in contact with the target object.

The target object may be a processing chamber of a substrate processing apparatus which performs a specific process on a substrate.

Preferably, the target object may be a part in a processing chamber of a substrate processing apparatus which performs a specific process on a substrate.

The part in the processing chamber may be a mounting table which mounts the substrate in the processing chamber.

In accordance with another aspect of the present invention, there is provided a cooling unit for cooling a target object to a target temperature, including: a decompression chamber thermally connected to the target object; a spraying part which sprays a liquid heat medium having a temperature equal to or lower than the target temperature to an inner surface of the decompression chamber; an electric field generator which generates an electric field such that the heat medium sprayed from the spraying part is attached to the inner surface of the decompression chamber; a target object temperature detection part which detects a temperature of the target object; and an exhaust part which evacuates the decompression chamber such that the temperature detected by the target object temperature detection part becomes the target temperature.

In accordance with still another aspect of the present invention, there is provided a processing chamber for performing a specific process on a substrate, including: a decompression chamber formed in a wall of the processing chamber; a spraying part which sprays a liquid heat medium having a temperature equal to or lower than a target temperature to an inner surface of the decompression chamber; and an electric field generator which generates an electric field such that the heat medium sprayed from the spraying part is attached to the inner surface of the decompression chamber.

In accordance with further still another aspect of the present invention, there is provided a part in a processing chamber for performing a specific process on a substrate, including: a decompression chamber formed in the part; a spraying part which sprays a liquid heat medium having a temperature equal to or lower than a target temperature to an inner surface of the decompression chamber; and an electric field generator which generates an electric field such that the heat medium sprayed from the spraying part is attached to the inner surface of the decompression chamber.

In accordance with further still another aspect of the present invention, there is provided a cooling method for cooling a target object to a target temperature by using a decompression chamber thermally connected to the target object, including: spraying a liquid heat medium having a temperature equal to or lower than the target temperature to an inner surface of the decompression chamber; generating an electric field such that the sprayed heat medium is attached to the inner surface of the decompression chamber; and evacuating the decompression chamber such that a pressure in the decompression chamber is equal to or lower than a saturated vapor pressure of the heat medium at the target temperature.

Said evacuating the decompression chamber may comprise evacuating the decompression chamber such that the inner pressure of the decompression chamber becomes equal to the saturated vapor pressure of the heat medium at the target temperature.

In accordance with further still another aspect of the present invention, there is provided a cooling method for cooling a target object to a target temperature by using a decompression chamber thermally connected to the target object, including: spraying a liquid heat medium having a temperature equal to or lower than the target temperature to an inner surface of the decompression chamber; generating an electric field such that the sprayed heat medium is attached to the inner surface of the decompression chamber; detecting a temperature of the target object; and evacuating the decompression chamber such that the detected temperature becomes the target temperature.

In the present invention, the decompression chamber for cooling is thermally connected to the target object. The liquid heat medium having a temperature equal to or lower than the target temperature is sprayed to the inner surface, i.e., surface to be cooled, of the decompression chamber. The sprayed heat medium is attracted and attached to the inner surface of the decompression chamber by the electric field generated by the electric field generator. The exhaust part evacuates the decompression chamber such that the inner pressure in the decompression chamber becomes equal to or lower than a saturated vapor pressure of the heat medium at the target temperature, or equal to the saturated vapor pressure. Accordingly, the heat medium has a liquid phase before being attached to the inner surface of the decompression chamber, and the temperature of the heat medium attached to the inner surface is increased to exceed the target temperature, so that the heat medium is converted into a gas phase.

During the phase transition, the heat medium absorbs the latent heat needed to be vaporized from the target object, thereby cooling the target object. Further, the heat medium can be effectively attached to the inner surface of the decompression chamber by a Coulomb force. Accordingly, it is possible to reduce an amount of the heat medium required for vacuum vaporization cooling compared to that needed in a configuration of simply spraying the heat medium. Further, since there is no need to spray an extra heat medium contrary to a case in a configuration of simply spraying the heat medium, it is possible to sufficiently reduce the pressure in the decompression chamber and effectively cool the target object. Further, since it is possible to reduce the amount of the heat medium delivered, it is possible to reduce energy consumption of a pump for delivering the heat medium.

Further, the cooling method of the present invention includes spraying a liquid heat medium, generating an electric field, and evacuating a decompression chamber. The steps may be performed in a random order, or may be performed almost at the same time.

In the present invention, the heat medium is electrically charged by friction between the nozzle of the spraying part and the heat medium. Atomized and charged particles of the misty heat medium repel each other by a Coulomb force. Accordingly, the heat medium is attracted and attached, in fine particles, to the inner surface of the decompression chamber. That is, in a case where the sprayed heat medium is not electrically charged, particles of the heat medium are aggregated by surface tension, and it is difficult for the heat medium to reach the inner surface of the decompression chamber. However, in a case where the heat medium is electrically charged, it is possible to prevent particles of the heat medium from being aggregated. Accordingly, it is possible to effectively attach the heat medium to the inner surface of the decompression chamber.

In the present invention, a voltage is applied to the spraying part by the voltage application part, so that the heat medium can be electrically charged. The effects obtained by electrically charging the heat medium are the same as the above-described effects.

In the present invention, the decompression chamber is formed in the target object. Accordingly, it is possible to effectively cool the target object. Further, it is possible to reduce the size of the cooling unit.

In the present invention, the decompression chamber is provided outside the target object and is thermally connected to the target object by contact between the decompression chamber and the target object. Accordingly, it is possible to cool a target object in which the decompression chamber cannot be formed.

In the present invention, a processing chamber of a substrate processing apparatus for performing a specific process on a substrate is cooled.

In the present invention, a part in the processing chamber of the substrate processing apparatus for performing a specific process on a substrate is cooled.

In the present invention, a mounting table for mounting a substrate in the processing chamber of the substrate processing apparatus is cooled.

In the present invention, the temperature of the target object is detected by the target object temperature detection part, and the exhaust part evacuates the decompression chamber such that the detected temperature becomes equal to or lower than the target temperature.

Further, the cooling method of the present invention includes spraying a liquid heat medium, generating an electric field, detecting a temperature and evacuating a decompression chamber. The steps may be performed in a random order, or may be performed almost at the same time.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention will become apparent from the following description of embodiments, given in conjunction with the accompanying drawings, in which:

FIG. 1 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit in accordance with an embodiment of the present invention;

FIG. 2 schematically shows configurations of an exhaust part and a cold water producer;

FIG. 3 is a flowchart showing steps of a cooling process of the controller;

FIG. 4 is a constitutional diagram conceptually showing vacuum vaporization cooling conditions;

FIG. 5 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit in accordance with Modification Example 1;

FIG. 6 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit in accordance with Modification Example 2;

FIG. 7 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit in accordance with Modification Example 3; and

FIG. 8 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit in accordance with Modification Example 4.

DETAILED DESCRIPTION OF THE EMBODIMENT

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings which form a part hereof.

FIG. 1 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit 6 in accordance with the embodiment of the present invention. The semiconductor manufacturing apparatus in accordance with the embodiment of the present invention is, e.g., a parallel plate type plasma etching apparatus. Further, the parallel plate type plasma etching apparatus is an example of a plasma processing apparatus, and it is not limited thereto. The semiconductor manufacturing apparatus includes a hollow cylindrical processing chamber 1. The processing chamber 1 is formed of, e.g., aluminum, and is grounded.

A disc-shaped mounting table 2, which mounts a semiconductor wafer W thereon and also serves as a lower electrode, is placed at an approximately central bottom portion of the processing chamber 1 through a disc-shaped insulator 21. The mounting table 2 is formed of, e.g., aluminum, and has a decompression chamber 60 therein. The decompression chamber 60 is connected to each part of the cooling unit 6 which cools the mounting table 2, as a target object to be cooled, to be maintained at a target temperature. The decompression chamber 60 forms a part of the cooling unit 6. The mounting table 2 is cooled by the cooling unit 6, so that the semiconductor wafer W mounted on the mounting table 2 is cooled to be maintained at a process temperature. Further, a high frequency power supply 4 is connected to the mounting table 2 to apply a high frequency power for generating a bias voltage to the mounting table 2. In this case, the target temperature is a control target temperature of the mounting table 2. Ideally, the target temperature coincides with the process temperature at which the semiconductor wafer W is controlled to be maintained. However, considering the thermal resistance of the mounting table 2 and the semiconductor wafer W or the like, the target temperature may be set to be lower than the process temperature.

Further, an upper electrode 3 is provided at an approximately central top portion of the processing chamber 1 to face the mounting table 2. An annular insulator 14 is interposed between the processing chamber 1 and the upper electrode 3. A high frequency power supply 5 for generating a plasma is connected to the upper electrode 3. Further, the upper electrode 3 is formed in a hollow shape to form a gas shower head having a plurality of processing gas supply holes (not shown) on a surface facing the mounting table 2. A processing gas supply pipe 31 for supplying a processing gas to the upper electrode 3 is provided at the center of an upper surface of the upper electrode 3. The upper electrode 3 functions as the gas shower head to supply a processing gas into the processing chamber 1.

Further, as a gas exhaust unit, a gas exhaust pipe 12 is connected to, e.g., a side surface adjacent to a bottom surface of the processing chamber 1. The processing chamber 1 is configured to be vacuum evacuated by a vacuum pump (not shown) provided on a downstream side of the gas exhaust pipe 12. Further, the gas exhaust unit may be configured such that gas is exhausted from the bottom portion of the processing chamber 1.

Further, a transfer port 11 for transferring the semiconductor wafer W therethrough is formed on a side surface of the processing chamber 1. The transfer port 11 is configured to be opened and closed by a gate valve 13.

The decompression chamber 60 formed in the mounting table 2 is a cylindrical chamber having a circular bottom surface portion, a peripheral surface portion and a circular top surface portion. The bottom surface portion of the decompression chamber 60 has a discharge port formed at an appropriate location to discharge gas and water from the decompression chamber 60.

The cooling unit 6 includes a controller 61 for controlling an operation of each constituent part. The controller 61 is a micro computer having, e.g., a CPU. The CPU is connected to a storage unit storing a computer program needed for an operation of the controller 61, or various types of information such as a process temperature needed for a semiconductor manufacturing process. The CPU is also connected to an input/output unit for inputting/outputting various types of information and a control signal, and the like.

Further, the cooling unit 6 includes a temperature controller 62, a spraying part 64, an exhaust part 65, a cold water producer 651, a water supply pump 66, a flow rate control valve 67 and an electric field generating power supply 68, which are needed for cooling the mounting table 2 that is a target object to be cooled. Although a case where the exhaust part 65 employs an ejector vacuum pump will be described mainly as an example in the following embodiment, a combination of a separator for separating water and a rotary pump may be used as will be described later, and any exhaust device having substantially the same function may be used.

The temperature controller 62 controls the temperature of cold water, supplied from the cold water producer 651 that will be described later, to be maintained at a spraying temperature in accordance with a control signal transmitted from the controller 61, and supplies the temperature-controlled water to the spraying part 64 through a line 63 a. In this case, the spraying temperature is required to be higher than a temperature at which sprayed mist-like water is frozen, and lower than a temperature at which the water is evaporated before reaching an inner surface of the decompression chamber 60. A minimum temperature at which the mist-like water is evaporated is the target temperature. In other words, the spraying temperature is required to be higher than the freezing temperature, and also equal to or lower than the target temperature. Further, an inner wall of the mounting table is cooled by vaporization heat when the mist is vaporized. Accordingly, a cooling effect does not depend on the temperature of the mist.

The spraying part 64 is provided at the peripheral surface portion of the decompression chamber 60. The spraying part 64 is connected to the temperature controller 62 through the line 63 a. The spraying part 64 has a mist nozzle (nozzle) 64 a for spraying liquid phase water (heat medium) of the spraying temperature supplied from the temperature controller 62 to the inner surface, e.g., top surface portion, of the decompression chamber 60. The heat medium is electrically charged by friction between the mist nozzle 64 a and the water. By forming the mist nozzle 64 a using, e.g., stainless steel, resin or the like, it is possible to electrically charge the sprayed water. The magnitude and polarity of the charged sprayed water depend on a positional relationship between a material forming the mist nozzle 64 a and water in the triboelectric series. As they are more separated in the triboelectric series, the water is charged with a larger quantity of electric charge. Further, if the water is located on the negative side of the triboelectric series compared to the material of the mist nozzle, the water is negatively charged, and if the water is located on the positive side of the triboelectric series compared to the material of the mist nozzle, the water is positively charged. Further, charges are generated in not only the water but also the mist nozzle by friction between the mist nozzle and the water. Accordingly, the spraying part 64 is grounded in order to prevent the mist nozzle from being continuously electrically charged.

The electric field generating power supply (electric field generator) 68 is a direct current (DC) power supply for generating an electric field to attach the water sprayed from the spraying part 64 to the inner surface, e.g., top surface portion, of the decompression chamber 60. For example, a linear or sheet-shaped conductive member (electric field generator) 68 a in a floating state is provided at the top surface portion side of the decompression chamber 60. By applying a voltage to the conductive member 68 a, it is possible to generate an electric field directed from the inside of the decompression chamber 60 to the top surface portion of the decompression chamber 60, or an electric field directed from the top surface portion of the decompression chamber 60 to the inside of the decompression chamber 60. As an installation method of the conductive member 68 a, the conductive member 68 a may be installed on the top side of the decompression chamber 60 to serve as the top surface portion, and the top surface portion may be isolated from the other portion, and then a voltage may be applied thereto. In this case, in order to avoid DC conduction between the conductive member 68 a and the mounting table 2, the inner surface of the decompression chamber 60 of the top side at which the conductive member 68 a is installed, is required to be DC isolated by an insulation member 68 b such as an insulation film. Further, in order to prevent the conductive member 68 a from being exposed to the sprayed water, the surface of the conductive member 68 a facing inside the decompression chamber 60 may be covered with, e.g., a dielectric film, and a ground electrode corresponding thereto may be provided at, e.g., the inner bottom portion of the decompression chamber 60 to generate an electric field. In this case, preferably, the ground electrode may have a structure in which the ground electrode is interposed between dielectric materials, and may be DC isolated from the mounting table 2 without being exposed to the sprayed water.

The electric field is generated such that the water sprayed from the spraying part 64 is attracted to the top surface portion of the decompression chamber 60. If the water is positively charged, the electric field is generated such that the electrostatic potential at the inside of the decompression chamber 60 is higher than the electrostatic potential at the top surface portion. If the water is negatively charged, the electric field is generated such that the electrostatic potential at the inside of the decompression chamber 60 is lower than the electrostatic potential at the top surface portion.

FIG. 2 schematically shows configurations of the exhaust part 65 and the cold water producer 651. The exhaust part 65 is configured such that, generally, a liquid is vaporized into vapor, and gas present in a vessel intended to be evacuated is sucked and evacuated by a suction force generated when the vapor is discharged at a high speed. In the ejector vacuum pump of the present invention, water is used as liquid. The exhaust part 65 configured as the ejector vacuum pump includes a reservoir 65 d storing the water supplied through a line 63 d, a pump 65 h for pumping the water in the reservoir 65 d through lines 65 g and 65 i, a vacuum vessel 65 j for generating water vapor from the pumped water, an ejector nozzle 65 b for ejecting the water vapor supplied from the vacuum vessel 65 j through a line 65 k, a suction chamber 65 a having the ejector nozzle 65 b, and a diffuser 65 c, wherein the respective constituent parts are connected to each other and the suction chamber 65 a communicates with a line 63 b. Particularly, the reservoir 65 d is provided with a condenser 65 e for condensing the water vapor discharged from the decompression chamber 60 of the mounting table 2. Further, an overflow line 65 f is provided at an appropriate location of the reservoir 65 d.

In the exhaust part 65 configured as described above, a vacuum suction force is generated in the suction chamber 65 a by supplying the water of the reservoir 65 d to the ejector nozzle 65 b by the pump 65 h and circulating the water through the diffuser 65 c and the reservoir 65 d. The exhaust part 65 discharges gas and liquid phase temperature adjusting medium, i.e., water, from the decompression chamber 60 by the vacuum suction force. Specifically, in case of cooling the mounting table 2, the exhaust part 65 discharges not only the vaporized water (i.e., water vapor) but also non-vaporized water (i.e., liquid water) from the decompression chamber 60. Further, in case of heating the mounting table 2, the exhaust part 65 discharges riot only water vapor but also condensed liquid water from the decompression chamber 60.

The cold water producer 651 includes a cold water reservoir 651 a communicating with the suction chamber 65 a, a line 651 f for supplying water from the reservoir 65 d to the cold water reservoir 651 a, a float valve 651 g provided on the line 651 f, a pump 651 c for producing cold water to pump the water in the cold water reservoir 651 a through a line 651 b, a freezing chamber 651 d for cooling the pumped water, and an evaporator 651 e provided in the cold water reservoir 651 a. A part of the water sprayed from the evaporator 651 e is evaporated as water vapor by absorbing the latent heat required for the evaporation from the remaining water during the evaporation, thereby cooling the remaining sprayed water.

The cold water reservoir 651 a communicates with the line 63 c and is configured such that the cold water is delivered from the cold water reservoir 651 a to the temperature controller 62 through the line 63 c.

The water supply pump 66 is provided in the line 63 c. The water supply pump 66 is, e.g., a diaphragm pump, which is driven in accordance with a control signal transmitted from the controller 61 to supply the water cooled in the cold water producer 651 to the temperature controller 62.

The flow rate control valve 67 is provided in the line 63 c between the temperature controller 62 and the water supply pump 66. The flow rate control valve 67 controls the flow rate of the water delivered from the water supply pump 66 in accordance with the control signal transmitted from the controller 61, and delivers the flow rate-controlled water to the temperature controller 62.

The cooling unit 6 further includes a target object temperature detection part 69 a, a pressure detection part 69 b, a flow rate detection part 69 c, and a water temperature detection part 69 d. The target object temperature detection part 69 a is, e.g., a thermocouple temperature gauge embedded in an appropriate location in the mounting table 2 as a target object to be cooled. The target object temperature detection part 69 a detects the temperature of the mounting table 2 and outputs information on the detected temperature to the controller 61. The pressure detection part 69 b is connected to the line 63 b to detect a pressure in the decompression chamber 60 and outputs information on the detected pressure to the controller 61. The flow rate detection part 69 c detects the flow rate of the water flowing in the line 63 c, and outputs information on the detected flow rate to the controller 61. The water temperature detection part 69 d detects the temperature of the water before being ejected by the nozzle after flowing through the line 63 and being temperature controlled by the temperature controller 62, and outputs information on the detected water temperature to the controller 61. The controller 61 acquires the information on the mounting table temperature, pressure, flow rate, and water temperature through the input/output unit, and carries out a cooling process based on the acquired information. Then, the controller 61 outputs a control signal for controlling the operation of each of the exhaust part 65, the water supply pump 66 and the flow rate control valve 67 to the corresponding part. Further, the semiconductor wafer W is mounted on the mounting table 2 to achieve high thermal transfer efficiency therebetween, and the temperature control is performed through the mounting table 2.

FIG. 3 is a flowchart showing steps of a cooling process of the controller 61. As an ideal case, the target temperature is assumed to be equal to the process temperature. The controller 61 drives the exhaust part 65, the water supply pump 66 and the like. Further, an electric field for mist attraction is generated in the decompression chamber 60 by the electric field generating power supply 68 (step S11). Further, the controller 61 reads the process temperature required for a semiconductor manufacturing process, the control target temperature, from a storage unit (not shown) (step S12). Subsequently, the controller 61 detects the temperature of the mounting table 2 by using the target object temperature detection part 69 a (step S13).

Then, the controller 61 sets the process temperature as the target temperature and determines whether the temperature of the mounting table 2 detected by the target object temperature detection part 69 a exceeds the process temperature (step S14). Hereinafter, the temperature of the mounting table 2 (target object to be cooled) detected by the target object temperature detection part 69 a is referred to as a detected temperature. If the detected temperature is equal to or lower than the process temperature (step S14: NO), i.e., if the detected temperature is equal to or lower than the target temperature, it is no longer necessary to cool the mounting table 2, and thus the controller 61 controls the flow rate control valve 67 to be in a closed state (step S15).

If it is determined that the detected temperature exceeds the process temperature (step S14: YES), the controller 61 determines a set water temperature and a set flow rate of the water to be sprayed to the top surface portion of the decompression chamber 60 (step S16), and determines a set pressure in the decompression chamber 60 (step S17). Here, the set water temperature, the set flow rate and the set pressure are described.

FIG. 4 is a phase diagram conceptually showing vacuum vaporization cooling conditions. In FIG. 4, a horizontal axis represents the temperature, and a vertical axis represents the pressure. A curve in a graph in FIG. 4 represents a saturated vapor pressure Psv(T) of water. Psv(T) is a function of temperature T. If the detected temperature exceeds a process temperature T1, it is necessary to reduce the temperature of the mounting table 2. Accordingly, the controller 61 determines the set pressure corresponding to the set temperature in a temperature-pressure area represented by hatching (the set temperature being set to be equal to or lower than the process temperature T1 (=target temperature)). Although the set temperature may be set to be equal to the process temperature T1, the set temperature may be set to be slightly lower than the process temperature T1 such that the temperature of the mounting table quickly converges on the target temperature (=process temperature T1). The set water temperature of water sprayed from the nozzle is controlled to become the above-described spraying temperature. In this case, the set water temperature (=spraying temperature) is required to be lower than the temperature corresponding to the saturated vapor pressure when the set water pressure is assumed to be the saturated vapor pressure, i.e., the set temperature, in order to prevent the ejected water from being completely evaporated during the ejection. However, since the water is frozen if the set water temperature is too low, it is required to set the set water temperature at a temperature preventing the water from being frozen. After the water ejected from the nozzle reaches the top surface portion of the decompression chamber 60, the temperature of the water is increased due to the top surface portion. Since the temperature of the water becomes higher than the set temperature, the water is vaporized. During the vaporization, heat is absorbed by the vaporized water from the top surface portion, and thus the temperature of the top surface portion is lowered. In this way, the series of steps from spraying to vaporization are repeated until the top surface portion is cooled to the process temperature T1. Further, if the mounting table 2 is cooled to be maintained at the target temperature, it is no longer necessary to cool the mounting table 2 to be maintained at the temperature lower than the target temperature. Accordingly, ideally, it is not necessary to set the pressure of the decompression chamber 60 to be lower than the saturated vapor pressure at the process temperature. However, actually, thermal resistance exists in the heat transfer between the semiconductor wafer W and the mounting table 2 whose temperature is controlled, and thus a temperature gradient may be developed. Accordingly, considering such situation, the target temperature may be set to be lower than the process temperature, and the set pressure may be set to be lower than the saturated vapor pressure at the process temperature, and equal to the saturated vapor pressure at the target temperature. Further, in the temperature control using a feedback, the temperature may converge on the target temperature while fluctuating near the target temperature. Accordingly, the set pressure may be lower than the saturated vapor pressure at the target temperature. The flow rate of water may be determined such that the inner pressure of the decompression chamber 60 does not deviate from the above temperature-pressure range by vaporization of the water sprayed to the top surface portion. That is, the set flow rate may be determined such that the amount of the water ejected is kept less than the amount of water vapor that can be evacuated by the vacuum pump.

Specifically, the controller 61 may store in advance a corresponding table of the process temperature (=set temperature), the set water temperature, the set flow rate and the set pressure. Then, the controller 61 may determine the set water temperature, the set flow rate and the set pressure based on the process temperature read in step S12 and the above table.

The controller 61 having completed step S17 controls the opening degree of the flow rate control valve 67 based on the set flow rate such that the flow rate becomes the set flow rate (step S18).

Then, in order to make the temperature of the water equal to the set water temperature (=spraying temperature), the controller 61 feedback-controls the operation of the temperature controller 62 based on the set water temperature while the water temperature is detected by the water temperature detection part 69 d, and controls the water temperature to become the set water temperature (step S19). Then, in order to make the inner pressure of the decompression chamber 60 equal to the set pressure, the controller 61 feedback-controls the operation of the exhaust part 65 based on the set pressure while the pressure is detected by the pressure detection part 69 b, and controls the pressure to become the set pressure (step S20). After reaching the set flow rate, the set water temperature and the set pressure by the control of step S18 and the feedback control of steps S19 and S20, the mounting table 2 is cooled to the process temperature based on the set flow rate, the set water temperature and the set pressure, and the cooling process is set to be in a steady state if necessary such that the process temperature is continuously maintained while a semiconductor manufacturing process is performed on the semiconductor wafer W. While cooling is in progress, the temperature of the mounting table 2 may become lower than the target temperature. However, the water having a temperature equal to or lower than the target temperature at the set pressure is not evaporated. Accordingly, further cooling is not performed and supercooling does not occur.

As the semiconductor manufacturing process performed on the semiconductor wafer W under specific processing conditions, e.g., plasma process such as etching process is completed, when step S20 or S15 of the cooling process is completed, the controller 61 determines whether a next process is performed to carry out a semiconductor manufacturing process using a different process temperature (step S21). If it is determined that the next process is performed (step S21: YES), the controller 61 controls such that the process returns to step S12, and acquires a new process temperature to repeat the above cooling process.

If it is determined that the next process is not performed (step S21: NO), the controller 61 determines whether or not the plasma process is completed (step S22). If it is determined that the plasma process is not completed, for example when another semiconductor wafer W is continuously processed under the same processing conditions (step S22: NO), the controller 61 controls such that the process returns to step S13. If it is determined that the plasma process is completed (step S22: YES), the controller 61 stops the cooling process. Further, in a case where the process returns to step S13 as described above, when there is no need to repeatedly determine the set water temperature, the set flow rate and the set pressure due to no change in the temperature of the mounting table 2, the process may return to step S18 instead of step S13.

In the cooling unit 6, the cooling method and the mounting table 2 forming the cooling unit 6 in accordance with the embodiment of the present invention, the water sprayed to the top surface portion of the decompression chamber 60 is evaporated at a low temperature by absorbing the latent heat of the evaporation from the mounting table 2 to thereby cool the mounting table 2. Accordingly, it is possible to achieve uniform cooling of the semiconductor wafer W and high responsiveness compared to a conventional cooling method.

Further, the water sprayed into the decompression chamber 60 can be made to be efficiently attracted to the top surface portion by the electric field. Furthermore, it is possible to reduce the amount of water required for vacuum vaporization cooling and cool the mounting table 2 with high efficiency. Moreover, it is possible to promote energy saving by reducing the amount of water required for vacuum vaporization cooling.

Further, compared to a configuration in which the heat medium is simply sprayed without using the electric field, there is no need to spray extra water. Accordingly, it is possible to sufficiently reduce the pressure of the decompression chamber 60 and effectively cool the mounting table 2.

Further, since the water sprayed from the spraying part 64 is electrically charged by friction between the water and the mist nozzle 64 a, atomized misty water particles repel each other by a Coulomb force. Accordingly, the sprayed water is attracted and attached, in fine particles, to the top surface portion of the decompression chamber 60. Thus, it is possible to effectively attach the water to the inner surface of the decompression chamber 60 and cool the mounting table 2.

Further, since the decompression chamber 60 is formed in the mounting table 2, it is possible to efficiently cool the mounting table 2 and promote space saving of the cooling unit 6.

Further, although the example in which the decompression chamber 60 is formed in the mounting table 2 has been described in the embodiment, the decompression chamber 60 may be provided in another part, which is arranged in the processing chamber 1, to form the cooling unit in accordance with the embodiment of the present invention. An example in which the decompression chamber is provided in the wall of the processing chamber will be described later.

Modification Example 1

FIG. 5 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit 106 in accordance with Modification Example 1. The semiconductor manufacturing apparatus and the cooling unit 106 in accordance with Modification Example 1 have the same configurations as those of the above-described embodiment, and further include a voltage application part 164 b to apply a voltage to the spraying part 64. The voltage application part 164 b is a DC power supply for electrically charging the water sprayed from the spraying part 64. In a case where the electric field directed from the inside of the decompression chamber 60 toward the top surface portion of the decompression chamber 60 is generated by the electric field generating power supply 68, a positive potential is applied to the spraying part 64. In a case where the electric field directed from the top surface portion of the decompression chamber 60 toward the inside of the decompression chamber 60 is generated by the electric field generating power supply 68, a negative potential is applied to the spraying part 64.

In Modification Example 1, by applying a voltage to the spraying part 64, it is possible to effectively charge the water sprayed from the exhaust part 65, and allow the water to be attracted and attached to the top surface portion of the decompression chamber 60.

Modification Example 2

FIG. 6 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit 206 in accordance with Modification Example 2. The semiconductor manufacturing apparatus and the cooling unit 206 in accordance with Modification Example 2 have the same configurations as those of the above-described embodiment, and are different from those of the above embodiment in that a decompression chamber 260 and a spraying part 264 are further provided in the wall of a processing chamber (target object to be cooled) 201, so that a desired location of the inner wall of the processing chamber 201 is cooled. The desired location of the inner wall of the processing chamber 201 may be a part of the inner wall, or the whole inner wall. The difference will be mainly described below.

The processing chamber 201 of the semiconductor manufacturing apparatus in accordance with Modification Example 2 has the decompression chamber 260 formed in the wall thereof to cool the processing chamber 201. Further, in FIG. 6, although the decompression chamber 260 is formed in a part of the processing chamber 201 for the convenience of illustration, it is merely exemplary. The decompression chamber 260 may be provided over the entire circumference of the processing chamber 201, or may be provided in a part of the top portion or the other portion of the processing chamber 201. That is, the decompression chamber 260 may be provided in a portion corresponding to the location which is required to be cooled in the inner wall of the processing chamber 201. Further, the decompression chamber 260 may have a structure projecting toward the outside instead of being provided in the wall of the processing chamber 201. The bottom portion of the decompression chamber 260 has a discharge port formed at an appropriate location to discharge gas and water from the decompression chamber 260. The discharge port is connected to the exhaust part 65 through a line 263 b.

The spraying part 264 is provided on the outer peripheral side of the decompression chamber 260, and is connected to the temperature controller 62 through the line 63 a. The spraying part 264 has a mist nozzle 264 a, and a detailed configuration thereof is the same as that of the above-described embodiment.

An electric field generating power supply 268 is a DC power supply for generating an electric field to attach the water sprayed from the spraying part 264 to the inner surface, e.g., inner peripheral surface, of the decompression chamber 260. A linear or sheet-shaped conductive member 268 c in a floating state is provided on the inner peripheral wall of the decompression chamber 260. By applying a voltage to the conductive member 268 c, it is possible to generate an electric field in a direction from a high potential to a low potential. That is, it is possible to generate an electric field directed from the outer peripheral side of the decompression chamber 260 to the inner peripheral side of the decompression chamber 260, or an electric field directed from the inner peripheral side of the decompression chamber 260 to the outer peripheral side of the decompression chamber 260. In order to avoid DC conduction between the conductive member 268 c and the mounting table 2, an insulation member 268 d such as an insulation film is provided in the wall of the decompression chamber 260, on which the conductive member 268 c is installed.

Further, in the same way as in the above-described embodiment, the electric field generating power supply 268 includes a conductive member 268 a and an insulation member 268 b to generate an electric field such that the water serving as a heat medium is attracted to the top surface portion of the decompression chamber 60.

In Modification Example 2, is possible to cool a location of the inner wall of the processing chamber 201, which is required to be cooled, and prevent the wall of the processing chamber from having a high temperature by a plasma process. In addition, in case of using a gas for chemical vapor deposition (CVD) to perform film formation at a high temperature, it is possible to prevent the growth of deposits on the inner surface of the processing chamber by cooling to a low temperature. Further, in an etching process in which a reaction product tends to be deposited on a low temperature location, by providing a protection wall on the inner wall, the protection wall providing excellent heat transfer between the protection wall and the inner wall and being detachable from the inner wall, the reaction product may be positively deposited on the protection wall and prevented from being deposited on other locations.

In Modification Example 2, the inner wall to be cooled may be a top plate. Generally, in case of cooling a susceptor, side wall or the like, in order to prevent a location other than a desired location from being unnecessarily cooled and prevent a reduction in cooling efficiency, it is required to prevent, as much as possible, the mist from being accumulated in liquid phase in the bottom portion of the decompression chamber. However, in case of cooling the top plate, since a target object is the bottom portion of the decompression chamber, the mist may be sprayed toward the bottom portion and may be allowed to fall by gravity.

Modification Example 3

FIG. 7 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit 306 in accordance with Modification Example 3. The cooling unit 306 in accordance with Modification Example 3 has a first and a second decompression chamber 360 and 370 for cooling the mounting table 2 as a target object to be cooled and a processing chamber (target object to be cooled) 301, respectively, wherein the first decompression chamber 360 is provided at an external of the mounting table 2 and the second decompression chamber 370 is provided at an external of the processing chamber 301.

The first decompression chamber 360 is formed in a hollow cylindrical shape, and fixed onto an approximately central bottom portion of the processing chamber 301. The mounting table 2 is fixed on the top of the first decompression chamber 360 through the disc-shaped insulator 21. The first decompression chamber 360 has the same configuration as the decompression chamber 60 of the above-described embodiment. A first spraying part 364 is provided on a peripheral surface portion of the first decompression chamber 360. Further, a first conductive member 368 a isolated by a first insulation member 368 b and in a floating state is provided on the top of the first decompression chamber 360. A voltage is applied to the first conductive member 368 a by an electric field generating power supply 368. Further, the bottom portion of the first decompression chamber 360 has a discharge port for discharging gas and water from the first decompression chamber 360. The gas and water discharged from the discharge portion are supplied to the exhaust part 65 through a line 363 b.

The second decompression chamber 370 has a configuration in which the decompression chamber 260 of Modification Example 2 is provided on the outer peripheral side of the processing chamber 301. A second spraying part 371 is provided in the second decompression chamber 370. A second conductive member 368 c isolated by a second insulation member 368 d and in a non-contacting state is provided in the inner peripheral wall of the second decompression chamber 370. A voltage is applied to the second conductive member 368 c by the electric field generating power supply 368. Further, a discharge port is formed at the bottom portion of the second decompression chamber 370 to discharge gas and water from the second decompression chamber 370. The gas and water discharged from the discharge port are supplied to the exhaust part 65 through the line 363 b.

In Modification Example 3, the same effects as those of the above-described embodiment can be obtained.

Modification Example 4

FIG. 8 schematically shows a configuration of a semiconductor manufacturing apparatus including a cooling unit in accordance with Modification Example 4. Although a case where the ejector pump is used as the exhaust part has been described in the above embodiment, as shown in FIG. 8, a rotary pump 465 may be used instead of the ejector pump. In this case, a separator 465 a for separating liquid water is installed on the upstream side of the rotary pump 465. The water separated by the separator 465 a is first stored in a drain tank 465 b, and then may be circulated again to a spraying nozzle through the water supply pump 66 or may be discharged directly. Otherwise, the water may be discharged directly without using the drain tank 465 b. Even in the recirculation through the water supply pump 66, the water may be circulated directly without passing through the drain tank 465 b if there is no need for flow rate control. However, in case of using the drain tank 465 b, there is an advantage of discharging excessive water. Further, if an insufficient amount of water is supplied, supplementary water may be supplied, separately from the water supplied from the separator 465 a, through the line 63 d. If it is sufficient with the circulation of the water supplied from the separator 465 a, normally, the water may not be supplied through the line 63 d. The pump used on the downstream side of the separator 465 a is not limited to the rotary pump, and may be any pump capable of being used at a pressure ranging from the atmospheric pressure to a low vacuum level.

In accordance with the above described embodiment and modifications thereof, the heat medium sprayed into the decompression chamber thermally connected to the target object is attracted to the inner surface of the decompression chamber by the electric field. Accordingly, it is possible to reduce an amount of heat medium required for vacuum vaporization cooling, and cool the target object with high efficiency.

While the invention has been shown and described with respect to the embodiments, it will be understood by those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims. 

1. A cooling unit for cooling a target object to a target temperature, comprising: a decompression chamber thermally connected to the target object; a spraying part which sprays a liquid heat medium having a temperature equal to or lower than the target temperature to an inner surface of the decompression chamber; an electric field generator which generates an electric field such that the heat medium sprayed from the spraying part is attached to the inner surface of the decompression chamber; and an exhaust part which evacuates the decompression chamber such that a pressure in the decompression chamber is equal to or lower than a saturated vapor pressure of the heat medium at the target temperature.
 2. The cooling unit of claim 1, wherein the spraying part has a nozzle for spraying the heat medium into the decompression chamber, and the heat medium is electrically charged by friction between the nozzle and the heat medium.
 3. The cooling unit of claim 1, further comprising a voltage application part which applies a voltage to the spraying part.
 4. The cooling unit of claim 1, wherein the decompression chamber is formed in the target object.
 5. The cooling unit of claim 1, wherein the decompression chamber is provided outside the target object and is in contact with the target object.
 6. The cooling unit of claim 1, wherein the target object is a processing chamber of a substrate processing apparatus which performs a specific process on a substrate.
 7. The cooling unit of claim 1, wherein the target object is a part in a processing chamber of a substrate processing apparatus which performs a specific process on a substrate.
 8. The cooling unit of claim 7, wherein the part in the processing chamber is a mounting table which mounts the substrate in the processing chamber.
 9. A cooling unit for cooling a target object to a target temperature, comprising: a decompression chamber thermally connected to the target object; a spraying part which sprays a liquid heat medium having a temperature equal to or lower than the target temperature to an inner surface of the decompression chamber; an electric field generator which generates an electric field such that the heat medium sprayed from the spraying part is attached to the inner surface of the decompression chamber; a target object temperature detection part which detects a temperature of the target object; and an exhaust part which evacuates the decompression chamber such that the temperature detected by the target object temperature detection part becomes the target temperature.
 10. A processing chamber for performing a specific process on a substrate, comprising: a decompression chamber formed in a wall of the processing chamber; a spraying part which sprays a liquid heat medium having a temperature equal to or lower than a target temperature to an inner surface of the decompression chamber; and an electric field generator which generates an electric field such that the heat medium sprayed from the spraying part is attached to the inner surface of the decompression chamber.
 11. A part in a processing chamber for performing a specific process on a substrate, comprising: a decompression chamber formed in the part; a spraying part which sprays a liquid heat medium having a temperature equal to or lower than a target temperature to an inner surface of the decompression chamber; and an electric field generator which generates an electric field such that the heat medium sprayed from the spraying part is attached to the inner surface of the decompression chamber.
 12. A cooling method for cooling a target object to a target temperature by using a decompression chamber thermally connected to the target object, comprising: spraying a liquid heat medium having a temperature equal to or lower than the target temperature to an inner surface of the decompression chamber; generating an electric field such that the sprayed heat medium is attached to the inner surface of the decompression chamber; and evacuating the decompression chamber such that a pressure in the decompression chamber is equal to or lower than a saturated vapor pressure of the heat medium at the target temperature.
 13. The cooling method of claim 12, wherein said evacuating the decompression chamber comprises evacuating the decompression chamber such that the inner pressure of the decompression chamber becomes equal to the saturated vapor pressure of the heat medium at the target temperature.
 14. A cooling method for cooling a target object to a target temperature by using a decompression chamber thermally connected to the target object, comprising: spraying a liquid heat medium having a temperature equal to or lower than the target temperature to an inner surface of the decompression chamber; generating an electric field such that the sprayed heat medium is attached to the inner surface of the decompression chamber; detecting a temperature of the target object; and evacuating the decompression chamber such that the detected temperature becomes the target temperature. 